Electromagnetic pick-up



Nov. 10, 1931. s. M CLATCHIE I ELECTROMAGNETIC PICK-UP Filed Dec.

7, 1929 2 Sheets-Sheet 2 m m w H I Sfanley IIIcfIaTc/rh A W HTTOITIIEYPatented Nov. 10, 1931 1 ITE /sures orm i? STANLEY mechanisms, or BERIN-WILMERSDORF, GERMANY ELEcrnoMliGN rro PICK-Ur ApplicationfiledDecembert, 1929'. Serial No. 412,489..

' This invention concerns electro-magnetic pick-ups and has for its mainobject to provide an improvedform of permanent-magnet in combinationwith the pick-up tone arm. Other objects will become apparent from thedescription. l

As is generally known, it is of advantage to have the magnetic field inelectrounagnetic pick-ups asin'tense as possible, without having to keeptheair gap between the armature and the pole pieces within too smalllimits in order to secure a satisfactory signal. With magnets of thesize and type at present in general use, it-hasjbeen found necessarytohold this air gap to from five-to eight thousandths' of an inch. Thisextremely small spacing involves delicate adjustment which is'neversecure, as the armature is practical considerations.

labile and liable tochange its position, due to ageing-of the rubbercushions which are used to position'it. It is therefore, in-general,"desirable to increase the size of. the permanent magnets u sedto set upthe magnetic field in phono ra-ph pick-ups. Thesize of the magnet is,owever, determined by It has heretofore been the universalcustom toinclude the magnet within the pick backward towards the tonearm'supportand' the use of clumsy pick-up heads is obviated.

Referring to the drawings,-Figure1 shows a top view .of a proposedembodiment of my invention?Figure 2-, a cross section on the lineAB ofFigure 1; Figure'3 shows. a section onthe line CD and Figured, atop"view'of the spool with its associatedholder. Figure 5 illustrates analternative arrangement embodying my invention. Fig. Gi'is a fragmentaltop View of the pick-up arrangement shownin'FigtS. p

In the preferred for m shown in Figure l, '1 is a U-shaped magnetextending; from the pick-up head to the tone arm support,- this magnetconstituting in itself the tone arm. The arm is pivoted onthe pin 2,which-is held in the bottom? of the 'casin 4. This casing is providedwithslots 5 an 6 for the passage of" the "tone arm. spring 7, engaging'extension 8' of-the'tone arm, serves to hold-the arm against thepivotandat the same time, to draw the portion of thetone arm passing through theslot 5 against the upperedge of said slot, so that'the arm as a whole isfirmly guided and prevented from oscillating with the phonograph needle.As is welliknown, it is important that the suprigid againstrneedleoscillations, in order to prevent thedistortion of lower frequencieswhich would result from movement-of the pick-up as a Whole.

porting structure for 'pick-ups should be The abovementioned"tonearm'extension consists of two halves 8 'and'8",heldtogether by rivets or screws 9. Between these' two halves, .isprovided a tubular recess, within whichis held the reciprocating pin 10which is pressed against the casing by spring 11-. On raising the tonearm to change: needles,

th'e'pin 10. engages under the projection' 12 ;in thecasing and holdsthe tone arm in an inclined position until it is desired to againlowerthe pickup upon the=record. "To do this, it is only necessary tomove thepick-up head a little to the right, when the pin disengages fromprojection 12, as will be evident from an inspection of Figure 1; 1 VThe pick-up headincludes the s 00115 held in the casing 16,Iwhichisprefera ly ofin'sulating material. 17 and 18 are pole-pieces' and 1-9a coverofthin material to keep foreign =-matter out of-the pick-up.Screws 20 securethe pick-up head with associatedpolepieces and cover'plate to the legs of the tone arm magnet. Leads from the magnet spoolare carried along the-tone arm legs and into the arm support 1 casing,being securedto the legs by small clamps 20' orrany othersuitableimeans. The armature system isde- .ber gaskets serve both aspositioning and damping members for the armature. The

armature and tone head structure just de-- scribed has been given onlyby way of illustration and it is understoodthat entirely difierentsystems might be combined with the novel form of magnet-tone arm whichconstitutes the main feature of my invention.

By way of illustrating an alternative method of carrying out myinvention, I have shown in Figures 5 and 6 the magnet ina form such asis current in the telephone receiver standard in theUnited States. The

outer casing tube constitutes in this case the tone arm proper, but themagnet is associated with and forms part of the tonearm structure. ThisI conceive to be the essence of the main feature of myfinvention.

It will be noted that inboth the embodiments of my inventionjustdescribed, the pick-uphead is greatly reduced in size and simplified bycomparison with the types now current. This compensates in manufacturingcost for the somewhat increased bulk of the tone arm. The increase insize and strength of the magnet combined, in'accordance with theinvention, with the tone arm, contributes to increased loudness andclarity of signal from the record.

While I have described my invention more or less specifically withreference to the drawings herein, it is obvious that I would haveitunderstood that my invention may be practical in many ways, withoutdeparting from the spirit and scope thereof, in attaining theobjectsherein set forth. i

What I claim to be secured by Letters Patent of the United States, is:

1. In combination with an ele'ctro-magnetic pick-up device, a-pick-uphead carrying a phonograph needle and a cooperating armature, a magneticstructure for'said armature having an extended portion pivotallyarranged to serve as a tone arm for said pickup head. i

2. 'In combination with an electro-magnetic pick-up device, a pick-uphead carrying a phonograph needle in operating position andagcoo'perating magnetic arm'atureof an extended magnet pivotallyarranged at one of its ends and carrying said pick-up head at theremaining end to serve as a supporting arm thereof and as an operatingmagnet of.

said armature. i 3.111 combination with'an electro-magnetic pickupdevice, a pick-up head including means for carrying a phonograph needlein operating position and a cooperating magnetic' armature associatedtherewith, a tone operating magnetic arm support, a magnet extendingfrom said pick-up head to said tone arm support, constituting a tone armand serving as an operating magnet for said armature.

4. In a device for transforming mechanical oscillations intocorresponding magnetic variations comprising in combination, a pickuphead including means for carrying a pickup needle in operating positionto be subjected to said mechanical oscillations and an armatureassociated therewith, a supporting member of said pickup, a magnetextending from said pick-up head to said supporting member to servesimultaneously as a supporting arm of said pick-up head and asoperatingmagnet of said armature. 5.;- In combination with anelectro-magnetic pick-updevice for phonographs and the like, a pick-uphead including means for carrying a phonograph needle in operatingposition and a cooperating magnetic armature associated therewith, atone arm support, a U- shaped magnet extending from said pick-up head tosaid support, to constitute a tone arm of said device and to serve asoperating magnet of said armature.

6. In combination with an electro-magnetic pick-up device forphonographs and thelike,

a pick-up head including means for holding I a phonograph needle invoperating position and a cooperating magnetic armature associatedtherewith, a tone arm'support having a casing, a magnet extendingfromsaid pickup head to said support, to serve simultaneously as a tonearmfor said pick-up head and as operating magnet of said armature, a'pinheld-at the bottom of said casing to pivot said magnet passing through aslot of said casing and means for resiliently holding said magnetagainst its pivot and at the same time to draw the portion of saidmagnet passing through said slot against the upper edge thereof. I

' 7. In combination with an electro-magnetic pick-up device forphonographs and the like, a pick-up head, including means for carrying aphonograph needle in operating position, a tone arm support having acasing, a tone arm extending from said pick-up. head to said support, apin held in the bottom of said casing for pivoting said tone arm passingthrough a slot of said casing, and means for resiliently holdingsaidtone arm against its pivot and at the same time, to draw the portionof said tone arm passing through said slot against one edge thereof.

8. In combination with an electro-magnetic device for phonographs andthe like, a pickup head including means for carrying a phonograph needlein operating position and a cooperating magnetic armature associatedtherewith, a tone arm support, a U-shaped magnet, pole pieces of saidmagnet cooperatively associated with said armature, said magnetextending from said pick-up head to said support to serve as atone armof said pick-up device.

9. In combination with an electro-magnetie device for phonographs andthe like, a pickup head including means for carrying a phonograph needlein operating position and a cooperating magnetic armature associatedtherewith, a tone arm support having a casing, a U-shaped magnet,pole-pieces of said magnet cooperatively associated with said armature,said magnet extending from said pick-up head to said support to serve asa tone arm of said pick-up device, a pin held in the bottom of saidcaslng to pivot said magnet at its U-shaped end, whereby the legs ofsaid magnet pass through slots of said casing, and means to resilientlyhold said magnet against its pivot and at the same time to draw theportion of one of said legs against the upper edge of its slot.

In testimony whereof I affix my signature.

STANLEY MOCLATCHIE.

